Method and apparatus for carrying out continuous thick chrome plating of bar, wire and tube, both externally and internally

ABSTRACT

A method and apparatus for bar electroplating including continuously supplying a plurality of bars successively; cleaning the surface of the bars to be plated; heating the bars up to a plating temperature and accomplishing the bar plating operation by feeding the bars along a straight path through an electrode immersed in an electroplating tank.

Un ted States Patent 1 1 1111 3,852,170 Angelini Dec 3, 1974 1 1 METHODAND APPARATUS FOR [56] References Cited CARRYING OUT CONTINUOUS THICKUNITED STATES P N CHROME PLATING F BAR, WIRE AND 781,867 2/1905Aylsworth 204/210 TUBE, BOTH EXTERNALLY AND 1,803,691 5/1931 Brockway204/210 INTERNALLY 2,756,205 7/1956 Rosenquistm 204/209 2,825,681 3 1958Johnston 1 ..204/28 [75] Invent: Sergm Angel, M113, Italy 3,616,28710/1971 Draghicescu et a]. 204/ [73] Assignee: B.E.S. BrevettiElettrogalvanici 3720595 3/1973 f' 204/206 superfiniture SDAI, 3,751,3448/1973 Angel1n1 204/26 Eh-L' ht t",L' ht t' Sc en lec ens em lee ens emPrimary Examiner-T. M. Tufariello Flledl 1973 Attorney, Agent, orFirm-Fidelman, Wolffe, Leitner 21 Appl. No.: 329,220 & Hmey ForeignApplication Priority Data Feb. 8. 1972 Italy 20337-A/72 [57] ABSTRACTRelated Application Data A method and a aratus for bar electroplatininclud- 63 PP s 1 1 fgg g g g r gzi 5 fig ing continuously supplying aplurality of bars succes- 9 A um sively; cleaning the surface of thebars to be plated; 5' d one heating the bars up to a plating temperatureand accomplishing the bar plating operation by feeding the $3 4 5 barsalong a straight path through an electrode im- [58] Field 61 Search204/210, 25, 27, 28, 206, mersed electroplatmg tank' 204/209v 21 Claims,22 Drawing Figures S: /////////////////////1// 1//////////// 1 ://2 k\&1\\\\\ \\k\\\\\\\\\\\\\\\\\\\\Y\ PATENTEU E 1974 SHEET 2 OF 5 mammal:3,852,170

SHEET NF 5 The present invention is a continuation-in-part ofapplication Ser. No. 89,428, filed Nov. 13, 1970, and now US. Pat. No.3,751,344, and application Ser. No. 261,419, filed June 9, 1972 nowabandoned.

This invention relates to a method and apparatus for electroplating,coating or metalization of general bars. More particularly, the presentinvention relates to chrome plating bars of circular cross-section aswell as those that are of different cross-section.

The invention will be hereinafter set forth and described with referenceto a method and apparatus for metal bar chromium plating. It should beunderstood, however, that the invention is not limited thereto and canbe extended and used to provide a metal coating on bars by anelectrolytical deposition process.

As is well known, in present bar chromium plating systems, provision ismade for a tank containing a chromium plating bath. The tank is longerthan the bars and the bars are immersed in the bath for a predeterminedtime period. These systems are extremely cumbersome and expensive due totheir size requirements for the tanks. Moreover, the chromium plating isaccomplished in a batch method with the resulting low hourly output ofchromium plated bars.

Further disadvantages arise due to scrap produced by an inability tochromium plate the portion of the bar gripped and clamped by the liftingapparatus required for immersion of the bars in the tank. Further, dueto the deflection of said bars caused by the weight thereof, thedistance between the electrodes and bars varies and non-uniformdeposition of the chromium coating or plating occurs. The thickness isnot uniform or constant longitudinally, increases from the center to theends and varies circumferentially in accordance with the arrangement ofthe electrodes within the chromium plating bath.

Therefore, an object of the present invention is to provide a method andapparatus for bar electroplating, and particularly chromium plating forbars and the like, capable of overcoming the above mentioneddisadvantages.

More particularly, the invention relates to a method and apparatus forcontinuously electroplating bars and the like.

Generally, the method according to the invention includes the steps ofcontinuously supplying a plurality of bars consecutively to anelectroplating bath; cleaning the surface of the bars to be plated;heating the bars up to a plating temperature and electroplating byfeeding the bars along a straight path through an electrode immersed inan electroplating bath.

Particularly, a first preheating step for each bar can be carried outupstream of the plating bath by utilizing the plating current. Then anext heating step can be carried out within the plating bath prior tothe plating step by heat transfer from the bath. The bars thus enter theplating electrode at a temperature substantially corresponding to thatof said plating bath.

More particularly, the present invention relates to a method forchromium plating either cylindrical or noncylindrical section bars,wherein the bars are continuously supplied to a chromium plating bath intwo or more straight paths parallel to and spaced apart from oneanother, so as to substantially increase the hourly output of the bath.

A further object of the present invention is to provide a method andapparatus for bar electroplating, and particularly for bar chromiumplating, wherein the spacing between the bar to be chromium plated andthe anode in the chromium plating bath is maintained constant so as tosubstantially improve the metal coating deposition on the bars bycontrolling coating thickness to very close tolerances. Thus, subsequentgrinding of the electroplated or chromium plated bars conventionally canbe avoided.

The invention is also directed to a general plating system, andparticularly to a chromium plating system for bars and the like, whereinthe floor space required is minimized in that the chromium plating tanklength is substantially less than that of the bars to be processed andwherein, by suitable expedients, tube or noncylindrical section bars ofdifferentdiameters can be processed. This is afforded by using specialseals at the common axis; (4) sealing means for the moving bars at eachof the passage openings in the tank to resist, and preferably prevent,any egress of processing liquid whereby a constant liquid level ismaintained; (5) means for supporting, guiding and successively feedingthe bars through said electroplating bath or tank along said axis; (6)means for causing a current to flow between said electrode and the barsto be plated; (7) means for cleaning and heating the bars to a platingtemperature upstream of the electrode in said tank; and (8) means for.feeding and recycling the processing liquid between the electroplatingtank and a supply reservoir while maintaining it at aconstanttemperature.

By adjusting and maintaining the processing liquid at a constanttemperature and by heating the bars prior to entering the platingelectrode, a smooth and constant plating operation is promoted, therebyproviding bars having substantially constant characteristics of thecoating layer produced along each of the bars and on different bars.

The system is also provided with means for recirculating the washingwater, as well as the processing liquid, for the bars at the tankoutlet. A means is also provided for purifying the fumes or vapors fromthe processing bath.

These and other features of the method and system according to theinvention will become more apparent from the following description whentaken in conjunction with the attached drawings, in which:

FIG. 1 is a general view of a system according to the invention which,due to drawing requirements, has been divided into three portionsjoining at the division lines aa and bb, the three portions beingindicated as 1A, 1B and 1C;

FIG. 2 is a view taken along line 22 of FIG. 1;

FIG. 3 is a partial sectional view showing, on an enlarged scale, adetail of the electroplating tank on the entry side for the bars;

FIG. 4 is a longitudinal sectional view of a box for the electrodecontact to the bars to be processed;

FIGS. 5 and 6 are longitudinal and cross-sectional views, respectively,showing a second embodiment of a box for the electric contact to thebars;

FIG. 7 is a longitudinal sectional view of a pneumatic sealing devicelocated at a passage opening for the bars in the processing tank.

FIG. 8 is a view taken along lin 8-8 of FIG. 7;

FIG. 9 is a side view showing a bar drawing device;

FIG. 10 is a front view of the device shown in FIG.

FIGS. 11, 12 and 13 are exploded, side and front views, respectively, ofa bar cleaning device for cylindrical bars;

FIG. l4 is a diagram of the device used for removal of the fumes andvapors from the electroplating bath;

FIGS. 15 and 16 are fragmentary cross-sectional and longitudinal views,respectively, of a modified system according to the invention;

FIG. 17 is a front view showing a particular scaling for non-circularsection bar electroplating FIG. 18 is a' vertical sectional view takenalong line 18-18 of FIG. 17; and

FIGS. 19 and 20 are different views for a detail of the sealing deviceshown in FIG. 17.

Referring now to FIGS. l-3 of the accompanying drawings, it will be seenthat a continuous electroplating system according to the invention,particularly for barchromium plating, comprises a tank designated as awhole at 29 which contains a processing liquid forming theelectroplating bath. The metal bars 10 which are to. be plated arecontinuously passed through this tank and are successively mechanicallyand/or electrically interconnected and fed along one or more straightpaths parallel to, and spaced apart from, one another by means of asuitable drawing device, such paths lying on a horizontal plate as shownin FIG. 2.

More particularly, in the course of their feeding, these bars 10 arecarried at both ends of the electroplating tank 29 by stands 1 l at thetop having a support or bracket 12 being carried at the upper end of avertical screw 13 which rotates in a nut screw 13', operable by handlebars 13" to adjust the correct height position of support 12 formaintaining said bars 10 at accurate rectilinear attitude.

The bars are connected together in accord with Pat. No. 3,751,344, bymeans of e.g. threaded or friction fittings. The fittings may beconductive or nonconductive depending on considerations such as barlength, etc. Also, the bars may be of circular crosssection, triangularcross-section, rectangular crosssection or other cross-section, howeverirregular in shape. Different seal means as disclosed herein may berequired for differing cross-sectional bars.

The drawing or feeding of bars 10 to the processing tank 29 isaccomplished by a drawing device which, in the example shown in FIG. 1,is located upstream of the processing tank 29 as shown by the barmovement direction according to arrow A, but which could also bedownstream of said tank.

The bar drawing device substantially comprises a first frame 16,adjustable in height and carrying the lower drawing rollers 17. Further,upper drawing rollers 18 are supported on a second .frame 19 adjustablein height relative to first frame 16. Thus, correct positioning andsmooth drawing of the bars can be accommodated independently of thediameter thereof.

For height adjustment of the first frame 16 carrying the drawing device,from FIGS. 1 and 2 it can be seen that vertical screws 14 are providedas rotatably carried by frame 16 and meshing with corresponding nutscrews 14' rotated in pairs by corresponding worms operable by a crank.

Similarly, frame 19 is adjustable in height relative to frame 16 byscrews 20 secured to said frame 16 and meshing with corresponding nutscrews 20 (FIG. 2), rotatably carried by frame 19 and rotatably drivenby suitable worms or the like operated by cranks 160.

The above mentioned lower and upper drawing rollers l7 and 18,respectively, are rotatably driven by a geared motor unit 21, carried byframe 19, through a speed variator 22, of which drive shaft 22' carriesat its ends pulleys or gear wheels driving, through belts or chains 22,the pulleys or gear wheels 161 and 162 of the bearing shafts of saiddrawing rollers 17 and 18. Thus, the drawing speed can be varied andadjusted in accordance with the diameter of the bars to be processed andthe thickness of the material to be formed on the bars.

As shown in FIG. 2, drawing rollers 17 and 18 are coated with a layer ofrelatively resilient material, have a circumferential grooveformedtherein for bar guiding, and are aligned with the feeding axis of thebars. This groove should be slightly distorted when in contact with thebar to increase thefriction surface,

thus avoiding slippage and allowing for accommodation of bars ofdifferent diameters.

The bar drawing device could be adapted for drawing one or more bars,such as parallel bars 10 shown in FIG. 2, or plural bars at one rolleras schematically shown in FIGS. 9 and 10, where the drawing rollers 17and 18 have been made with conical surfaces converging to the center inorder to increase the bar adhering surface. v

The bars, continuously fed to the processing bath in tank 29, first passthrough box 23 wherein electric contacts are arranged for connecting thebars to the negative pole of a DC. power supply. Thus, the bar portionbetween anode electrode 31 (FIG. 3) and the electrode 131 (FIG. 16) ischarged with the required current flow for the deposition of material,such as chromium, on bar 10. A similar contact box 23' may be providedat the outlet or downstream of tank 29, as shown in FIG. I.

The plating current flowing through the section of bar 10 between theupstream contact box 23 and the anode 31 is preheated by the current toa temperature determined by the electric resistance of the bar path andthe square of the intensity of current flowing through the bar.

It is important to provide a positive electric contact surface with thebars while interferring with the feeding thereof to the least extentpossible. This has been accomplished by the contact box of FIG. 4wherein the electric contact with bars 10 is provided by copper plaits24 arranged about the peripheral surface of the bar 10. The plaits 24are clamped against bar 10 by two opposing tile-like elements 25, thelatter being held in proximity to each other by resilient rings 25a orother suitable means and being of a predetermined internal shapecorresponding to the number of plaits 24 and the bar diameter.

Downstream of contact box 23, the bars pass through a cleaning device 26which comprises a sleeve containing an abrasive material mat or felt 27(as shown in the cut-away portion of FIG. 3) completely surrounding bar10. The material 27 cleans bar 10 by, e.g., rubbing.

In order to remove any possible impurities from said cleaning device andbar, the sleeve is supplied with hot water at a predetermined pressurethrough a conduit 28. The water continuously removes deposits from thebar surface or from the cleaning felt. The use of hot water for cleaningdevide 26 is advantageous since it helps retain bar 10 at its preheatedtemperature as mentioned above. Therefore, in order to collect waterdripping from cleaning device 26 or from a plurality of such cleaningdevices where the bars are fed along two or more parallel paths as shownin FIG. 2, a tank 27' is provided underneath the cleaning'device ordevices 26 as shown in FIG. 1B. This tank 27 collects the water comingout of cleaning device 26 and conveys it through a pipe 27 to acollection tank 40 which is provided with a net cover 41 at the topthereof for carrying a filter 41', so that impurities are retained onfilter 41. and conditioned water enters said tank 40. The water iswithdrawn from tank 40 through pipe 43 and recycled by pump 43'.

As stated, bars 10 pass through the tank 29 containing the plating bath.Therefore, passage openings for bars 10 provided on the opposite walls29' of the processing tank 29 are fitted with suitable sealing devices30 to resist,and possibly inhibit, any exit of processing liquid fromthe tank. Thus, a constant'liquid level L is maintained above bar 10 andtubular electrode 31 as shown in FIG. 3.

These sealing elements 30 will be further discussed in connection withcylindrical bars (FIG. 7) and noncylindrical section bars (FIGS. 17-20).

Upon continuously moving, the bars 10 enter the processing tank 29through the sealing device 30 on end wall 29, and travel'a section orlength h in the tank between the inlet opening and electrode 31. Duringthis travel, the bar 10 is heated up to the plating temperature,preferably the temperature of the processing liquid, by heat transferfrom the liquid. The bar then enters and passes through the perforatedtubular electrode 31 where the plating is carried out by deposition of alayer of predetermined thickness, depending on the bar feeding rate andthe intensity of the plating current.

The plated bars pass through a corresponding sealing device 30 in exittank wall 29' which is fully similar to the above mentioned devicenTheyare then washed with water supplied by a nozzle 34. The plated bars passthrough a second contact box 23, which also supplies current, so thatplating current is supplied at both ends of tank 29 and the bartemperature is partly retained at the tank outlet to aid in the dryingstep. Following contact boxes 23, the bars (carried by one or moresupporting stands 11) may be further processed as desired. 1

the washing water and conveying it through a conduit 44 to a collectiontank 45. Tank 45 is manually identical to tank 40 mentioned above and isprovided with a filtering device 41' and 42. The water is withdrawnDownstream of tank 29 and underneath the washing f, water nozzle 34, abasin 44 isprovided for collecting from tank 45 by means of a pump 46and supplied by a two-way valve 47 either to nozzle 34 or to an externalreservoir, according to process requirements.

Similarly, in order to collect any processing liquid lost from tank 29through sealings 30, collection basins 30' are provided upstream anddownstream from the tank under the seals. Conduits 30" collect the lostfluid and convey it to a cooling tank 32 for the processing liquid, theprocessing tank 29 usually being connected to tank 32 by a loop orclosed circuit.

More particularly, plating tank 29 is connected through a gated conduit35 to tank 32 wherein the liquid is maintained at a predetermined levelabove a cooling coil 32 suitably connected to a refrigerating system(not shown). Tank 32 is provided with a thermostat 36 driving therefrigerating system for automatic temperature control and a tap or cock38 for total discharge. It is also connected by a pipe 37 (partiallyshown in FIG. 1) with a tank (not shown) of a higher capacity than thatof the processing tank 29 which is connected through suitable pumps andpipes to tank 29 for the recycle of the processing liquid. Thus,processing tank 29 can be continuously supplied with processing liquidof the desired composition and temperature, as the addition of furtherelectrolyte can be directly effectedto the above mentioned general ormajor tank. The use of the cooling coil 32' for the liquid exiting fromprocessing tank 29 is required since the processing liquid will, in thecourse of plating operation, be heated and thus have to be cooled priorto recycling for correct control of the processing bath temperature.

The sealing devices 30 onthe end walls 29' of the processing tank may beof any type, e.g., the pneumatic seals more fully described inconnection with FIG. 7.

When the sealing devices 30 are of the pneumatic character, the systemis provided with a compressed air supply (not shown), this supply beingconnected through a conduit 48 to the pressure regulator 50 anddistributor 49 which, in turn, is connected to several pneumatic sealingdevices.

As shown in FIG. 1, the processing tank 29 is covered with a suctionhood 51 and 151 which, as shown also in FIG. 14, is connected by exhaustfan 153, conduit 152, and fume removing device 154 to a stack forconveying the vapors to atmosphere.

As shown in FIG. 14, conduit 152 has an intermediate section 152'sloping to the hood for condensate return, as indicated by the brokenarrow. Thus, thorough purification of the fumes or vapors from theprocessing tank can be provided along with recovery of the electrolytecarried by such fumes by water washing. The wash water exits from device154 through a bottom conduit 155 and can be recycled.

Refering now to FIGS. 5 and 6 of the attached drawings, a differentembodiment of the contact box will be described. In the embodiment of'FIGS. 5 and 6, the contact box comprises a hollow cylindrical body 230which has two sealing devices 25 at the ends thereof, such as those'ofthe pneumatic character hereinafter described, through which bars 10continuously pass. A chamber 25" is formed by sealing devices 25' andcylinder 230, with ingress and egress being provided by upper aperture23a, the chamber thus being sealed with respect to the passing of bars10. A copper strap cathode C is passed through upper aperture 23a ofchamber 25 takes on the circular shape of the container body, and joinsitself outside aperture 23a. By

introducing mercury M (FIG. 6) into the space of chamber 25", positiveelectrical contact is provided along the bar circumference for theplating current.

A longitudinal section of a pneumatic sealing sleeve useful at the inletand outlet openings for the bars in processing tank is shown in FIG. 7.In this Figure, the sealing sleeve substantially comprises a hollowcylindrical'body 30, coaxially with cylindrical bars 10, through whichthe bars to be processed pass. At its ends, hollow cylindrical body 30has circular openings 56 coaxial with the bar passage. A tubular plasticacid resistant material 57 e.g., an acid resistant rubber, is attachedand sealed to openings 56 at its ends and, along with body 30, formsahermetically sealed annular chamber 58. This chamber 58 communicateswith a pressurized air supply through a conduit 59 distributor 49,pressure regulator 50, and conduit 48 (see FIG. 18). Thus, by passingbars through tubular diaphragm 57 in the sealing sleeve 30 and supplyingchamber 58 with air pressure, diaphragm 57 is urged toward the surfaceof bar 10 and provides a positive sealing for the processing liquid intank 29. Moreover, while providing for a seal on bar 10, diaphragm 57will not inhibit the sliding thereof. The use of a pneumatic sealingsleeve also allows for the accommodation of bars .of different diameterswithout the replacement thereof. However, it is apparentthat for bars ofsubstantially different diameters, sealing sleeves of different sizesshould be employed.

Sealing device 30, and more particularly the above mentioned sealingsleeve, can be fixedly attached to end walls 29' of the processing tankwhen the latter is to be used for electroplating the same type of barsat all times, or can be detachably and readily, replaceably secured (asshown in FIG. 8) when the material to be plated varies. As shown in thisFigure, sealing device 30 can be carried by a plate 60 and positionedwithin a channel or U-shaped seating 61 formed along the edge of asaddle-like notch 61 provided on each wall 29 of the processing tank 29when in use. Thus,.one tank can be used for processing bars havingdifferent crosssectional shapes and sizes.

However, the sealing device 30 can also be of the plate type, asdescribed below in connection with a modified form of the invention. Ofcourse, along the edge 60 of tank 29 provision should be made for asuitable seal for the liquid in the tank.

Referring now to FIGS. 11, 12 and 13 of the attached drawings, anexemplary structure for the cleaning device 26 will be described.

As shown, this device comprises two yoke-shaped elements 62 ofsubstantially symmetricalconstruction, each having a semicircular notchcontaining an abrasive felt 27 or other appropriate material. The twoyoke-shaped elements 62 are attached to each other by any suitableclamping device, for example, resilient binding 63 shown in FIG. 13.Upper yoke-like element 62 is also provided with a conduit 28 foradmission of wash water, as above set forth. A bracket 64 partiallysurrounds upper yoke-like element 62 and is provided with an arm 65which is connected to the stem 66 of a pneumatic or oleodynamic type ofdouble-acting cylinder 67. Movement of the piston by fluid pressure froma source which is not shown provides reciprocating rotation foreffective operation of the cleaning device. If desired, cleaning device26 could be continuously rotated rather than alternatively rotated.

Referring now to FIGS. and 16, a schematic modified form of the systemaccording to the invention will be described. In these Figures, all ofthe devices or parts common to FIG. 1 have not been shown for the sakeof simplicity. As shown, the processing tank 116 has been herein placedwith a second tank 117 of a larger size in order to allow forelectroplating tubes, circular cross-section bars and non-circularcrosssection bars. Thus, a particular plate sealing device has beendesigned for the latter.

The bottom 116' of processing tank 116 is elevated from the bottom 117'of the outer tank and is supported by legs 118. Outer tank 117 is of ahigher capacity than the inner tank 116 and the liquid in tank 117 ismaintained at a level L below'the bar passage openings in its walls,while inner tank 116 is completely filled with the processing liquid.The processing liquid is maintained at a predetermined temperature byheating elements 119 and is continuously'recycled by means of pumps 120and 120 so that the liquid level in tank 116 is substantially constantand above the bars which are to be processed. i

In order to reduce heat loss in the processing liquid in outer tank 117,covering baffles 121 are provided between adjacent walls of the tanks.The baffles are located below openings 123 through the inner tank andare retained spaced apart from the inner tank adjacent the .openings toallow the passage into the bottom of tank 117 of the processing liquidwhich leaks from the sealing devices 126 and overflows from the top edgeof the inner tank. To this end, the upper edges 116" of inner tank 16adjacent the seals are relatively lower than the rest of the tank edges,so that the liquid exhaust and overflow will occur in this zone.

Of course, openings 122 and 123 in the two tanks should be aligned withone another along a common axis for the bar or section electroplatingoperation. A tubular anode 131 is located within inner tank 116 andcompletely'immersed in the processing solution.

The double tank can be used for electroplating bar stock where apneumatic sleeve sealing of the above described character could not beused. However, it is apparent that instead of the double tank system,the system as shown in FIG. 1 could be used, providing end tanks 30' ofhigher capacity than shown for collecting the processing liquid.

In FIGS; 17-20, a further embodiment for sealing processing tank 29 or116 when plating various crosssection bars is shown. As shown in theFigures, bar 138 is surrounded throughout its profile by a double row offlexible blades 139. The blades of each row are located at equal shortspacings from one another and staggered relative to the blades in theadjoining row, so that one blade 139 in a row will bridge the spacingbetween two adjoining blades 139 in the other row Thus, the wholeopenings 123 is obstructed by the double rows of blades interferringwith the exit of the processing liquid from inner tank 116, and thusallowing the maintenance of substantially constant liquid level in thetank, since the tank is continuously supplied with an amount of liquidequal to the amount of liquid existing laterally and at the bottom ofthe bars. Blades 139 are secured to edge 123' of opening 123 on threesides, while at the g top of the tank, the blades 139 are secured tolower edge 140' of a gate or sliding plate 140. The plate is slippedinto and positioned by grooves 124' (FIG. 17). By moving plate 140, theposition of blades 139 can be controlled, and thus the closure ofopening 123 can be regulated to control liquid exit. Plate 140 isprovided with means to fix its position (not shown) as desired, forexample, by clamping screws or other equivalent means. Further, as shownin FIG. 19, at the lower edge of opening 123 the blades will intersectone another and further inhibit liquid loss.

Opening 123 could also have the lower portion, as well as the blades onplate 140, in the form of oppositely corresponding arcs so as to directsaid blades 139 to the geometrical axis of the bars 138 to be processed.Of course, blades 139 of FIGS. 17-20 should be made of an acidresisting, relatively resilient and flexible material in order not to beattacked by the processing liquid in the tank and to maximize liquidretention.

Referring to FIG. 1, the operation of the apparatus according to theinvention is substantially as follows:

Bars are successively mechanically and/or electrically interconnectedand carried by stands 11. They are fed to processing tank 29 after firstpassing through the contact box 23, then through cleaning device 26, andfinally through seal 30 in tank 29. In the tank, the bars are immersedin the processing liquid contained in anode 31 and are coated byelectroplating. The coated bars emerge from end wall 29' of the tank,through seal 30 and are washed, dried and then further processed asdesired.

As mentioned above, in the course of the first travel path of each barbetween contact box 23 upstream of tank seal 30, a first preheating ofthe bar is effected at a lower temperature than the electroplatingtemperature by the flow of the electroplating current through the bar.Also, in the length or section h within the tank between end wall 29'and the tubular anode 31 adjacent thereto, a second heating step forbars 10 is effected so that the bar temperature is substantially thesame as that of the processing liquid in the electroplating bath. By wayof example, a'length or distance h of about 50cm (20 inches), dependingon the feed rate of the bar, usually provides for proper heating of thebar. The plating bath temperature may vary in accord with known ranges.

Thus, a process for operating under optimum working conditions isdisclosed herein, in which a continuous electroplating system functionswith high hourly output and produces coatings which are within stricttolerances along each bar and between different bars. Moreover, theparticular system herein described allows for the maintenance of asubstantially constant temperature in the bath and has the advantage ofavoiding any pollution because of the liquid recirculation and/or thepurification of the fumes or vapors from the processing bath.

What is claimed:

1. A method for continuously electroplating a plurality of elongatedbars in a plating comprising:

a. mechanically attaching said bars together by couplings of the samesection as said bars to provide a generally continuous electroplatablesurface;

b. serially cleaning said attached bars prior to plating by passing saidbars consecutively through a cleaning medium;

c. serially passing said bars into contact with an electrode wherebysaid bars are charged with anelectroplating current;

d. serially heating said bars to the temperature of said bath prior toplating;

e. serially passingsaid bars through said electroplating bath and in theproximity of an electrode whereby said bars are electroplated; and

f. serially passing the plated bars out of said bath.

2. The method of claim 1 wherein said preheating is effected by firstpreheating said bars outside said bath and by secondly preheating saidbars in said bath prior to'the plating step.

3. The method of claim 2 wherein said first preheating is effected bysaid electroplating. current.

4. The method of claim 3 wherein said second preheating is effected bythe contact of said bath with said bar prior to electroplating.

5. The method of claim 3 wherein said mechanical connection isadditionally an electrical connection.

6. The method of claim 1 wherein said electrode in said bath is atubular electrode positioned co-axially with said bars.

7. The method of claim 1 wherein said bars are additionally cleanedafter passageout of said bath.

8. The method of claim 7 wherein said cleaning after plating includeswashing.

9. An apparatus for continuously electroplating a plurality of elongatedbars comprising:

a. means for serially mechanically attaching said bars together;

b. aligning means positioning said attached bars along an axis;

c. cleaning means prior to electroplating for cleaning said alignedbars;

d. drive means causing said bars to traverse the line of said axis; 7

e. a plating tank containing plating liquid and having seal means on twoends .thereof positioned coaxially with the axis of said bars wherebysaid bars pass serially into said tank through first seal means,

through said tank and out of said tank through said sealmeans;

f. heating means for said bars for heating said bars prior toelectroplating in said tank to the temperature of said plating liquidprior to electroplating;

g. a first electrode positioned outside said tank and a second elongatedelectrode positioned inside said tank whereby said electrodes cooperateto provide an electroplating current to plate said bar with material insaid plating liquid, said electrodes being positioned coaxially withsaid bar, and said first electrode being in electrical contact with saidbar before said bar enters said tank while said second electrode isspaced from said bar.

10. The apparatus of claim 9 wherein said heating means includes thecurrent passed along said bars by said electrodes.

11. The apparatus of claim 9 further including second cleaning means forcleaning said plated bars.

12. The apparatus of claim 9 further including recycle means forrecycling lost plating liquid to said plating tank.

13. The apparatus of claim 9 wherein said drive means includes upper andlower rollers in contact with said bars, means for adjustablypositioning said rollers, and means driving at least one of saidrollers.

14. The apparatus of claim 13 wherein said rollers 18. The apparatus ofclaim 9 wherein said tank is closed at its top by a hood connected to afume removing means.

19. The apparatus of claim 12 wherein said recycle means includes asecond tank of greater capacity than said plating tank and pump meansfor effecting said recycling, said plating tanks being arranged in saidsecond tank so that fluid lost from said plating tank is retained bysaid second tank.

20. The apparatus of claim 9 wherein said first electrode comprises acopper electrode arranged around said bars and held in electricalcontact therewith by clamping means peripherally of said bars.

21. The apparatus of claim 9 wherein said first electrode includes ahollow cylindrical body arranged coaxially with said bars and havingseal means at the ends thereof, said seal means and said body forming achamber, said chamber containing mercury and having a charged electricalconnection in contact therewith whereby said connection and said mercurycooperate to charge said bars.

1. A METHOD FOR CONTINUOUSLY ELECTROPLATING A PLURALITY OF ELONGATEDBARS IN A PLATING COMPRISING: A. MECHANICALLY ATTACHING SAID BARSTOGETHER BY COUPLINGS OF THE SAME SECTION AS SAID BARS TO PROVIDE AGENERALLY CONTINUOUS ELECTROPLATABLE SURFACE; B. SERIALLY CLEANING SAIDATTACHED BARS PRIOR TO PLATING BY PASSING SAID BARS CONSECUTIVELYTHROUGH A CLEANING MEDIUM; C. SERIALLY PASSING SAID BARS INTO CONTACTWITH AN ELECTRODE WHEREBY SAID BARS ARE CHARGED WITH AN ELECTROPLATINGCURRENT; D. SERIALLY HEATING SAID BARS TO THE TEMPERATURE OF SAID BATHPRIOR TO PLATING; E. SERIALLY PASING SAID BARS THROUGH SAIDELECTROPLATING BATH AND IN THE PROXIMITY OF AN ELECTRODE WHEREBY SAIDBARS ARE ELECTROPLATED; AND F. SERIALLY PASSING THE PLATED BARS OUT OFSAID BATH.
 2. The method of claim 1 wherein said preheating is effectedby first preheating said bars outside said bath and by secondlypreheating said bars in said bath prior to the plating step.
 3. Themethod of claim 2 wherein said first preheating is effected by saidelectroplating current.
 4. The method of claim 3 wherein said secondpreheating is effected by the contact of said bath with said bar priorto electroplating.
 5. The method of claim 3 wherein said mechanicalconnection is additionally an electrical connection.
 6. The method ofclaim 1 wherein said electrode in said bath is a tubular electrodepositioned co-axially with said bars.
 7. The method of claim 1 whereinsaid bars are additionally cleaned after passage out of said bath. 8.The method of claim 7 wherein said cleaning after plating includeswashing.
 9. An apparatus for continuously electroplating a plurality ofelongated bars comprising: a. means for serially mechanically attachingsaid bars together; b. aligning means positioning said attached barsalong an axis; c. cleaning means prior to electroplating for cleaningsaid aligned bars; d. drive means causing said bars to traverse the lineof said axis; e. a plating tank containing plating liquid and havingseal means on two ends thereof positioned co-axially with the axis ofsaid bars whereby said bars pass serially into said tank through firstseal means, through said tank and out of said tank through said sealmeans; f. heating means for said bars for heating said bars prior toelectroplating in said tank to the temperature of said plating liquidprior to electroplating; g. a first electrode positioned outside saidtank and a second elongated electrode positioned inside said tankwhereby said electrodes cooperate to provide an electroplating currentto plate said bar with material in said plating liquid, said electrodesbeing positioned coaxially with said bar, and said first electrode beingin electrical contact with said bar before said bar enters said tankwhile said second electrode is spaced from said bar.
 10. The apparatusof claim 9 wherein said heating means includes the current passed alongsaid bars by said electrodes.
 11. The apparatus of claim 9 furtherincluding second cleaning means for cleaning said plated bars.
 12. Theapparatus of claim 9 further including recycle means for recycling lostplating liquid to said plating tank.
 13. The apparatus of claim 9wherein said drive means includes upper and lower rollers in contactwith said bars, means for adjustably positioning said rollers, and meansdriving at least one of said rollers.
 14. The apparatus of claim 13wherein said rollers have a resilient surface with a circumferentialgroove therein.
 15. The apparatus of claim 12 wherein said recycle meansfurther includes a reservoir pump means and plating liquid cooling meansin said reservoir.
 16. The apparatus of claim 9 further including athird electrode downstream of said second electrode and of oppositepolarity than said second electrode.
 17. The apparatus of claim 9wherein said second electrode is spaced from first seal means in saidtank.
 18. The apparatus of claim 9 wherein said tank is closed at itstop by a hood connected to a fume removing means.
 19. The apparatus ofclaim 12 wherein said recycle means includes a second tank of greatercapacity than said plating tank and pump means for effecting saidrecycling, said plating tanks being arranged in said second tank so thAtfluid lost from said plating tank is retained by said second tank. 20.The apparatus of claim 9 wherein said first electrode comprises a copperelectrode arranged around said bars and held in electrical contacttherewith by clamping means peripherally of said bars.
 21. The apparatusof claim 9 wherein said first electrode includes a hollow cylindricalbody arranged coaxially with said bars and having seal means at the endsthereof, said seal means and said body forming a chamber, said chambercontaining mercury and having a charged electrical connection in contacttherewith whereby said connection and said mercury cooperate to chargesaid bars.